Olefinic composition with high octane decreasing the level of pollutants emissions in automotive vehicles

ABSTRACT

Dimerized branched olefins having from 5 to 12 carbon atoms obtained by controlled dimerization as of olefinics from having from 3 to 5 carbon atoms are blended with commercial fuel pools to increasing octane rank and decrease pollutant emissions.

FIELD OF THE INVENTION

[0001] This invention relates to the incorporation of a blend of branched olefins having from 5 to 12 carbon atoms in a fuel pool to increase octane and decrease the level of pollutant emissions.

BACKGROUND OF THE INVENTION

[0002] Prior to strict environmental regulations, polymerization gasoline containing a high percentage of light olefins (from 3 to 6 carbon atoms) was used. However, such olefins produce a large amount of pollution emissions (NOx, CO, HC).

[0003] Controlled dimerization of low molecular weight olefins produces branched iso-olefins, for example, olefins with eight carbon atoms such as: trimethyl-pentenes and dimethyl-hexenes (TMP=and DMH=), mainly, which have a higher octane rank (RON above 100) than the corresponding branched iso-paraffins, trimethyl-pentanes and dimethyl-hexanes (TMP and DMH). However the use of olefins in commercial fuels has been restricted (<10% vol), due to its polluting nature.

[0004] Common olefin polymerization processes have been widely studied. For example, Mexican Patent No. 147332 entitled “Improved Process For Low Molecular Weight Olefin Polymerization”, which issued Nov. 15, 1982, discloses an improved procedure for low molecular weight olefin polymerization using a phosphoric acid on a silica catalyst, while Mexican Patent No. 155578 entitled “Propylene Polymerization Process to Obtain Polymerization Gasoline”, which issued Mar. 29, 1988, discloses propylene and/or butene polymerization for obtaining polymerization fuel, also using an upgraded catalyst based on phosphoric acid supported on silica. The disclosures of such Mexican patents are hereby incorporated by reference in their entireties.

[0005] Mexican Patent No. 149066 entitled “Upgraded Catalytic Composition for Low Molecular Weight Olefin Polymerization”, which issued Aug. 17, 1983, and Mexican Patent No. 156181, entitled “Process for the Preparation of an Improved Catalyst to Obtain Propylene Tetramer”, which issued on May 27, 1988, relate to olefin polymerization by means of a phosphoric acid on silica catalyst. The disclosures of such Mexican patents are hereby incorporated by reference in their entireties.

[0006] The dimerized products are thereafter hydrogenated to produce branched paraffins, which are permitted in the fuel pool. In this connection, reference is made to XVII Catalysis Ibero American Symposium, Porto, Portugal, July 2000: “Obtaining High Octane Ecological Type Fuels Through Intermediate Olefins Hydrogenation”; 17 North American Catalysis Society Meeting, Toronto, Canada, June 2001: “Catalytic Conversion of C₄ Olefins to High Octane Fuels by Means of the Catalytic Dimerization and Hydrogenation of C₈”.

SUMMARY OF THE INVENTION

[0007] In accordance with the present invention, a gasoline fuel formulation has been discovered comprising between about 5 and about 15 percent by volume of a blend of branched olefins having from 5 to 12 carbon atoms obtained by the dimerization of olefins having from 3 to 5 carbon atoms. The fuel formulation of the present invention provides a fuel having a higher octane rating and a decreased pollutant emissions level when used as a gasoline fuel in the internal combustion engine of automotive vehicles, as compared to a similar gasoline fuel formulation containing the same percentage of lower molecular weight olefins, rather than the dimerized olefins of the present invention.

[0008] Accordingly to another embodiment of the present inventnion, a process for the production of a fuel formulation comprises admixing between about 5 and about 15 percent by volume of a blend of branched olefins having from 5 to 12 carbon atoms obtained from the dimerization of olefins having from 3 to 5 carbon atoms and added directly without further treatment, for example, hydrogenation of the dimerized olefins, into a commercial gasoline fuel pool. When used as a fuel in the internal combustion engine of automotive vehicles, a fuel formulation is provided by the present invention having a higher octane rating and a lower pollutant emissions level, as compared to a similar fuel formulation containing the same percentage of lower molecular weight olefins, rather than the dimerized olefins of the present invention.

[0009] Thus, the present process incorporates branched olefins having a high octane rank that complies with the ecological reqirements when the dimerized olefin product composed of branched olefins having 5 to 12 carbon atoms and preferably 8 carbon atoms obtained from the olefin dimerization containing from 3 to 5 carbon atoms, with preferably mainly 4 carbon atoms, is incorporated into a gasoline or reformulated fuel “pool”. Thus, the present olefinic composition becomes a functional part in the “pool” of commercial-type fuels, such as a gasoline pool, increasing its octane rank and contributing to decreasing the level of nitrogen oxide (NOx) emissions, carbon monoxide (CO) and hydrocarbons (HC).

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Referring to the drawings which form a part of this original disclosure in which:

[0011]FIG. 1 shows the comparative effect of dimerized olefins on NOx emissions;

[0012]FIG. 2 shows the comparative effect of dimerized olefins on carbon monoxide emissions; and

[0013]FIG. 3 shows the comparative effect of dimerized olefins on hydrocarbon emissions.

DETAILED DESCRIPTION OF THE INVENTION

[0014] According to the present invention, the olefinic composition product used in the gasoline fuel pool is produced by dimerizing light olefins containing from 3 to 5 carbon atoms, with mainly 4 carbon atoms being the preferred feedstock, under controlled olefin polymerization to produce a product containing branched olefins having from 5 to 12 carbon atoms, with mainly 8 carbon atoms being preferred, which product preferably has an octane rank (RON) between 90 and 130, a low Reid Vapor Pressure (<Rvp 5 psi), a low content of impurities, such as sulfur (<50 ppm), benzene (<1% vol.) and aromatic (<10% vol.); which decreases the level of pollutant emissions in automotive vehicles when the commercial type fuel formulation is included.

[0015] Any suitable light olefin feed stock contain olefins having 3 to 5 carbon atoms may be used in the dimerization process. A preferred feedstock is a C₄ FCC cut rich in C₄=olefins, for example, about 50 percent or more. The dimerization of the light olefins may be conducted using any suitable dimerization catalyst, which under process conditions can provide “controlled polymerization”, i.e., which can stop the polymerization at the dimerization stage. Additionally, the dimerization process of the present invention not only achieves high conversion to dimers, but is selective to produce isomers having the desired blending octane numbers, in particular, trimethylpentenes and dimethylhexenes.

[0016] Suitable catalysts useful in the present invention include solid acid catalysts and supported metal oxide catalysts. Suitable catalysts include any of the conventional solid acid catalysts, which catalysts are well known in the art and are disclosed, for example, in U.S. Pat. No. 6,486,339, the disclosure of which is hereby incorporated by reference in its entirety. Thus, solid acid catalysts, such as the SPA catalysts, the ZSM-5 zeolite catalysts, such as described in U.S. Pat. No. 4,849,186, the entire disclosure of which is incorporated by reference, may be employed in the present process. The supported metal oxide catalysts, in which a metal oxide, such as a Group VIII metal oxide is incorporated onto a support, may be used as well. For example, amorphous silica-alumina (ASA) supports may be used in combination with a metal oxide, including Group VIII metal oxides, including Ni (as Ni2+), which may also include a promoter, such as TaF5 (fluorotansil). Non-metallic catalysts including potassium carbonate and Nafion solid acid polymer, as well as Amberyst ion exchange resin may be used, if desired. The preferred catalyst is a supported metal oxide catalyst with phosphoric acid on silica being preferred. The H₃PO₄/S₁O₂ catalyst, well known as SPA, is especially preferred. Details of SPA (solid phosphoric acid) catalysts are well known in the prior art, such as U.S. Pat. No. 5,895,830, the entire disclosure of which is hereby incorporated by reference. Any suitable conditions may be employed to obtain controlled polymerization or dimerization of the light olefins, so long as the feed stock is maintained in the liquid phase. The conditions for liquid phase dimerization will vary depending on the type of catalyst used. For example, temperatures in the range of from about 100° C. to about 200° C., preferably from about 120° C. to about 140° C., pressures in the range of from about 300 to about 800 psia, preferably from about 450 to about 600 psia and space velocities of from about 0.5 to about 2.0 h⁻¹, preferably from about 0.7 to about 0.9 h⁻¹ WHSV are preferred. Such conditions allow, for example, selective dimerization of isobutylene present in the feed, as well as dimerization/isomerization of 1-butene and isomerization of 2-butenes.

[0017] The resulting dimerized olefin product is a high octane blending composition, so that it is important that the dimerized olefins are blended directly with the gasoline fuel pool without hydrogenation or any further treatment of the dimerized olefin product. The term “gasoline fuel pool” is intended to mean a blend of hydrocarbons useful as a fuel fraction in a spark ignited internal combustion engine, which term is well known in the art. Gasoline fuel pools comprise a number of components. The major components are reformulated gasolines, which normally comprise between 60% and 80% by volume of aromatic compounds, and FCC gasolines which typically contain 35% by volume of aromatic compounds but provide the majority of olefinic and sulfur-containing compounds present in the gasoline pools. The other components can be alkylates, with no aromatic or olefinic compounds, isomerized if at all, or non-isomerized light gasolines, which contain no unsaturated compounds, oxygen-containing compounds such as MTBE, and butanes. Such pools are described, for example, in U.S. Pat. No. 6,436,278, which is incorporated by reference in its entirety.

[0018] Provided that the aromatic compound content is not reduced below 35-40% by volume, the contribution of reformates to the gasoline pool remains high, typically 40% by volume. In contrast, an increased restriction to the maximum admissible amount of aromatic compounds to 20-25% by volume would cause a reduction in the use of reforming, and as a result the need to upgrade cuts composed of paraffins which are slightly or not isomerized, if at all, and with boiling points which correspond to those of a gasoline cut, by routes other than reforming.

[0019] The following Examples illustrate the present invention, but is not intended to limit the scope of the claimed invention.

[0020] The specifications in force for commercial fuels are presented in Table 1: TABLE 1 Specifications in force for Commercial Fuels Specifications Rank Reid Vapor Pressure (Rvp) 6.8-7.8 lb/pulg2 Sulfur <300 ppm Olefins <10% vol Aromatics <25% vol

[0021] Various streams were used to prepare the fuel formulations including: Catalytic, Alkylate, Reforming, Hydrotreated, Isomerizate and Methyl-tert.-Butyl Ether (known as MTBE), obtained from the Miguel Hidalgo PEMEX refinery in Tula, Hidalgo.

[0022] The average specifications from these streams not being limiting, are presented in Tables 2 to 7 which include the Research Octane Number (RON) as well, determined by applying the ASTM-D-2699 method. TABLE 2 Catalytic Stream Specifications Values Rvp (psi) 7.5 Sulfur (ppm) 1672 Olefins (% vol) 30.8 Aromatics (% vol) 17.3 RON 91.2

[0023] TABLE 3 Alkylate Stream Specifications Values Rvp (psi) 7.1 Sulfur (ppm) 112 Olefins (% vol) 0.0 Aromatics (% vol) 9.6 RON 96.2

[0024] TABLE 4 Reforming Stream Specifications Values Rvp (psi) 6.2 Sulfur (ppm) 0.0 Olefins (% vol) 0.0 Aromatics (% vol) 53.2 RON 96.3

[0025] TABLE 5 Hydrotreated Stream Specifications Values Rvp (psi) 1.9 Sulfur (ppm) 0.0 Olefins (% vol) 2.06 Aromatics (% vol) 18.1 RON 49.9

[0026] TABLE 6 Isomerizate Stream Specifications Values Rvp (psi) 12.8 Sulfur (ppm) 248 Olefins (% vol) 0.0 Aromatic (% vol) 0.0 RON 80.2

[0027] TABLE 7 MTBE Stream MTBE Values Rvp (psi) 7.2 Sulfur (ppm) 0.0 Olefins (% vol) 0.0 Aromatics (% vol) 0.0 RON 110

[0028] The dimerized olefinic composition average specifications used in the formulations and its composition regarding the number of carbon atoms from the present olefins, not being limiting, are shown in Tables 8 and 9. TABLE 8 Specifications for the Dimerized Specifications Values Rvp (psi) 2.15 Sulfur (ppm) 520 Olefins (% vol) 100 Aromatic (% vol) 0.0 Octane Rank 105

[0029] TABLE 9 Dimerized Composition OLEFINS % vol C₅ ⁼-C₆ ⁼ 0.66 C₇ ⁼-C₈ ⁼ 14.28 C₈ ⁼(TMP⁼) 55.32 C₈ ⁼(DMH⁼) 15.09 C₉ ⁼-C₁₂ ⁼ 14.65

[0030] The reformulated fuels, not being limiting but representative, were prepared using the streams of Tables 2 to 8, varying the olefin content to present lower values than the 5%, 10% limit and over the 15% limit.

[0031] For the No. 1, No. 2 and No. 3 fuel formulations hereinafter presented, the catalytic stream was used (Table 2), being the one presenting the higher light olefin content (C5=-C6=). Its composition and specifications are presented in Tables 10, 11 and 12, respectively. TABLE 10 No. 1 Fuel formulation (5% light olefins) Composition % vol Specifications Values Catalytic 15.30 Rvp (psi) 6.96 Dimerized 0.0 Sulphur (ppm) 320 Alkylate 32.37 Olefins (% vol) 5.39 Reforming 32.37 Aromatic (% vol) 20.53 Hydrotreated 3.00 Octane Number 90.9 Isomerizate 9.33 MTBE 7.63 Total 100

[0032] TABLE 11 No. 2 Fuel Formulation (10% light olefins) Composition % vol Specifications Values Catalytic 28.80 Rvp (psi) 6.97 Dimerized 0.00 Sulphur (ppm) 578 Alkylate 23.66 Olefins (% vol) 10.16 Reforming 23.66 Aromatics (% vol) 20.11 Hydrotreated 7.20 Octane Number 90.44 Isomerizate 9.05 MTBE 7.65 Total 100.00

[0033] TABLE 12 No. 3 Fuel Formulation (15% light olefins) Composition % vol Specifications Values Catalytic 43.20 Rvp (psi) 6.95 Dimerized 0.00 Sulphur (ppm) 852 Alkylate 15.15 Olefin (% vol) 15.24 Reforming 15.15 Aromatics (% vol) 19.96 Hydrotreated 11.00 Octane Number 90.0 Isomerizate 7.90 MTBE 7.60 Total 100.00

[0034] For the No. 4, No. 5 and No. 6 fuel formulations, the dimerized product (Table 8) using heavy branched olefins (C8=-C12=) was used, instead of the catalytic stream. Its composition and specifications are presented in Tables 13, 14 and 15 respectively. TABLE 13 No. 4 Fuel Formulation (5% heavy olefins) Composition % vol Specifications Values Catalytic 0.00 Rvp (psi) 6.96 Dimerized 5.27 Sulphur (ppm) 300 Alkylate 32.96 Olefins (% vol) 5.38 Reforming 38.33 Aromatic (% vol) 19.50 Hydrotreated 2.44 Octane Number 95.9 Isomerizate 13.35 MTBE 7.65 Total 100.00

[0035] TABLE 14 No. 5 Fuel Formulation (10% heavy olefins) Composition % vol Specifications Values Catalytic 0.00 Rvp (psi) 6.98 Dimerized 9.77 Sulphur (ppm) 300 Alkylate 26.25 Olefins (% vol) 9.95 Reforming 36.20 Aromatic (% vol) 18.58 Hydrotreated 4.52 Octane Number 95.9 Isomerizate 15.63 MTBE 7.63 Total 100.00

[0036] TABLE 15 No. 6 Fuel Formulation (15% heavy olefins) Composition % vol Specifications Values Catalytic 0.00 Rvp (psi) 6.94 Dimerized 14.73 Sulphur (ppm) 300 Alkylate 19.25 Olefins (% vol) 15.00 Reforming 34.26 Aromatic (% vol) 17.78 Hydrotreated 6.82 Octane Number 95.9 Isomerizate 17.32 MTBE 7.62 Total 100.00

[0037] For the formulations with the catalytic stream, No. 1, No. 2 and No 3 fuels, the specified value was exceeded for sulfur (refer to Table 1), due to the high content of this element in this stream. Contrary to the formulations with dimerized No. 4, No. 5 and No. 6 fuels, sulfur was added to get the limit value higher (300 ppm) to make them comparable.

[0038] The following illustrations exhaust emission tests (NOx, CO and HC) in an automotive vehicle:

[0039] The former formulations from fuel (1,2,3,4,5 and 6) were tested in a 1998 FORD automotive vehicle, standard transmission, 2.2 liter engine size and electric ignition, with a three way catalytic converter to monitor the emissions produced from each of them.

[0040] The exhaust emission evaluations were carried out three times, following the set up methodology in the NMX-AA-11-1993 Norm, similar to the FTP-75 Federal Procedure Test, stated by the Environmental Protection Agency (EPA) Regulations Code (CFR) from the United States of America. It consists on a cold start test carried out in a controlled atmosphere cell, wherein the temperature and other prevailing conditions can be kept within the specific limits. The vehicle simulates in a chassis dynamometer a 17.9 Km. trip in a typical city from the United States of America. The regulated exhaust emissions: NOx (nitrogen oxides), CO (carbon monoxide) and HC (hydrocarbons), are obtained in grams/kilometer by means of a mass balance for each of the pollutants taking the trip into account. The laboratory where these analysis are carried out is credited by the Test Laboratories Crediting National System (SINALP) presently EMA (Crediting Mexican Entity).

[0041] In the obtained results an emissions decrease is observed for the formulations where the Dimerized product was used (Table 16) TABLE 16 NOx, CO and HC emissions for each formulation Grams/Kilometer Fuel Formulation NOx CO HC No. 1 (5% light olefins) 0.29 1.21 0.05 No. 2 (10 light olefins) 0.31 1.37 0.06 No. 3 (15% light olefins) 0.29 1.63 0.06 No. 4 (5% heavy olefins) 0.25 0.95 0.04 No. 5 (10% heavy olefins) 0.27 1.10 0.06 No. 6 (15% heavy olefins) 0.26 1.19 0.06

[0042] The results are shown in FIGS. 1 and 3 in pollutant/kilometer grams regarding the olefins content (5, 10 and 15%), observing for the three cases, NOx emission (FIG. 1), CO emission (FIG. 2) and HC emission (FIG. 3), pollutant values decrease when used in the Dimerized (heavy olefins) formulation instead of Catalytic (light olefins).

[0043] Although the invention has been described with a certain degree of particularity, it is understood that the present disclosure has been made only by way of example. Thus, the scope of the invention should not be limited by the foregoing specification, but rather, only by the scope of the claims appended hereto. 

What is claimed is:
 1. A gasoline fuel formulation comprising between about 5 and about 15 percent by volume of a blend of branched olefins having from 5 to 12 carbon atoms obtained from the dimerization of olefins having from 3 to 5 carbon atoms, said fuel formulation having a having a high octane rating and a decreased pollutant emissions level when used as a fuel in the internal combustion engine of automotive vehicles, as compared to a similar gasoline fuel formulation containing the same percentage of lower molecular weight olefins.
 2. The gasoline fuel formulation of claim 1, wherein said additive comprises a blend of branched olefins having from 7 to 9 carbon atoms.
 3. The gasoline fuel formulation of claim 2, wherein said additive comprises trimethylpentenes and dimethylhexenes.
 4. The gasoline fuel formulation of claim 1, wherein said dimerization is conducted using a solid acid catalyst or a supported metal oxide catalyst.
 5. The gasoline fuel formulation of claim 4, wherein said catalyst is a phosphoric acid on silica catalyst.
 6. The gasoline fuel formulation of claim 4, wherein said dimerization reaction is conducted in the liquid phase.
 7. The gasoline fuel formulation of claim 6, wherein said dimerization reaction is conducted at a temperature in the range of from about 100° to about 200° C. and a pressure of from about 300 to about 800 psia and a space velocity of from a WHSV of from about 0.5 to about 2.0 h⁻¹.
 8. The gasoline fuel formulation of claim 5, wherein said dimerization reaction is conducted at a temperature in the range of from about 120° to about 140° C. and a pressure of from about 450 to about 600 psia and a space velocity of from a WHSV of from about 0.7 to about 0.9 h⁻¹.
 9. The gasoline fuel formulation of claim 5, wherein said gasoline fuel formulation has an octane rank between 90 and
 130. 10. A process for the production of a fuel formulation, which comprises admixing between about 5 and about 15 percent by volume of a blend of branched olefins having from 5 to 12 carbon atoms obtained from the dimerization of olefins having from 3 to 5 carbon atoms directly with a commercial gasoline fuel pool to produce a fuel formulation having a having a high octane rating and a decreased pollutant emissions level, when used as a fuel in the internal combustion engine of automotive vehicles, as compared to a similar fuel formulation containing the same percentage of lower molecular weight olefins.
 11. The process of claim 10, wherein said branched olefins have from 7 to 9 carbon atoms.
 12. The process of claim 11, wherein said branched olefins comprise trimethylpentenes and dimethylhexenes.
 13. The process of claim 10, wherein said dimerization is conducted using a solid acid catalyst or a supported metal oxide catalyst.
 14. The process of claim 13, wherein said dimerization is conducted in the liquid phase.
 15. The process of claim 14, wherein said dimerization reaction is conducted at a temperature in the range of from about 100° to about 200° C. and a pressure of from about 300 to about 800 psia and a space velocity of from a WHSV of from about 0.5 to about 2.0 h⁻¹.
 16. The process of claim 13, wherein said catalyst is a phosphoric acid on silica catalyst.
 17. The process of claim 16, wherein said dimerization reaction is conducted at a temperature in the range of from about 120° to about 140° C., and a pressure of from about 450 to about 600 psia, and a space velocity of from a WHSV of from about 0.7 to about 0.9 h⁻¹.
 18. The process of claim 17, wherein said gasoline fuel formulation has an octane rank between 90 and
 130. 19. The process of claim 10, wherein said blend of branched olefins are admixed with said gasoline fuel pool with hydrogenation.
 20. A process for the production of a fuel formulation, which comprises admixing between about 5 and about 15 percent by volume of a blend of branched olefins having from 5 to 12 carbon atoms with a commercial gasoline fuel pool to produce a fuel formulation having a having a high octane rating and a decreased pollutant emissions level, when used as a fuel in the internal combustion engine of automotive vehicles, as compared to a similar fuel formulation containing the same percentage of lower molecular weight olefins. 